The present invention relates to semiconductor pressure sensors and, more particularly, to a semiconductor pressure sensor which uses, as its detector element, a semiconductor sensor element capable of detecting any strain and/or stress that occurs to a thin-walled pressure receiving portion, and besides which is used as it is assembled to a housing body that partitions a pressure medium from outside.
Conventionally, as one type of pressure sensor, there has been known one which uses, as its pressure detecting element, a semiconductor sensor element (hereinafter, abbreviated simply as sensor element when appropriate) capable of detecting a strain and/or stress that occurs to a thin-walled pressure receiving portion by making use of the semiconductors' piezoresistance effect. Using this type of pressure detecting element makes it possible to detect with high accuracy the magnitude and/or change of a pressure that acts on the pressure receiving portion as a magnitude and/or change of a strain and/or stress and then to convert the detection result into an electric signal as an output.
Also, in such a semiconductor pressure sensor, there has been known one which is put into use in a state that the pressure sensor is assembled to a housing body serving as a pressure partition wall that partitions a pressure medium the pressure of which is to be detected and outside (i.e., one side on which the pressure medium is present and the other side on which the pressure medium is not present) from each other (see, for example, Japanese Patent Laid-Open Publication HEI 1-98936, SHO 64-61631 or HEI 1-169333).
FIG. 17 is a partial cross-sectional explanatory view showing the structure and the housing-body assembled state in an example of a prior art semiconductor pressure sensor (hereinafter, abbreviated simply as pressure sensor or sensor when appropriate).
This pressure sensor 201 according to the prior art example is of the so-called can-package (can sealing) type. The pressure sensor comprises an sensor assembly 205 which contains a unit body, although not shown in detail, comprising a semiconductor sensor element made of, for example, silicon, a pedestal seat made of silicon for joining and supporting the sensor element, a base member for joining and supporting the pedestal seat, and the like, and which is formed up by covering this integrally joined unit body with a cap, where a pressure introducing pipe 209 is integrally fixed to the sensor assembly 205.
By this pressure introducing pipe 209, a pressure medium in an interior Si of a housing body 210 is introduced into the sensor assembly 205. Also, via this pressure introducing pipe 209, the sensor assembly 205 is fixed to an adjustment circuit board 206. This adjustment circuit board 206 comprises a resistor circuit for adjusting electrical characteristics of the sensor element, a signal amplifying circuit and the like.
In addition, as to the arrangement of such an adjustment circuit board, there has been disclosed in, for example, Japanese Patent Laid-Open Publication HEI 1-150832, a can-package type semiconductor pressure sensor in which the adjustment circuit board is placed in proximity to the sensor chip so that the sensor can be downsized.
For the assembly of the pressure sensor 201 to the housing body 210, a straight through hole 210H is previously provided in the housing body 210 and a pressure introducing pipe 209 of the pressure sensor 201 is inserted into the through hole 210H, in which state the adjustment circuit board 206 is held to a holder 213 provided in the housing body 210. By this arrangement, the pressure sensor 201 is fixed to the housing body 210 via the adjustment circuit board 206. A seal member 219 (O-ring) is fitted on the periphery of the through hole 210H of the housing body 210, by which leakage of the pressure medium to outside So of the housing body 210 is prevented.
The housing body 210 is equipped with a system circuit board 211 on which electric circuits or the like for a system controlled by using a pressure detection result (more specifically, machines, appliances, devices or equipment or equipment systems using these) are mounted. This system circuit board 211 and the adjustment circuit board 206 of the pressure sensor 201 are electrically connected to each other by a lead wire 212. This lead wire 212 enables the feeding of power to the pressure sensor 201, the extraction of a detection signal from the pressure sensor 201, and the like.
In recent years, for pressure sensors themselves including an adjustment circuit board as described above as well as even the systems in which pressure detection is to be done, there has been a demand for even more compactness and lower costs further than before.
However, the conventional pressure sensor 201 as described above has a disadvantage in reducing the cost because it involves large number of parts and its construction is rather complicated.
Also, with regard to the assembly state to the housing body 210 on the system side, since the assembly is done with the adjustment circuit board 206 held to the holder 213 on the exterior side of the housing body 210, the system is protruded to a considerable extent to the outside So of the housing body 210. Thus, it is difficult to attain a compact assembled state.
In addition, particularly recently, there is a tendency to design higher integrations by incorporating into the sensor element itself an output adjusting circuit having resistor circuits or signal amplification circuits or the like for adjusting the electrical characteristics of the sensor element, instead of providing the adjustment circuit board separately from the sensor element. However, even with the use of such sensor element, the pressure sensor itself and systems in which pressure detection is to be done have been under a desire for even more compactness and lower costs.
The present invention having been accomplished in view of the above technical problems, an object of the invention is to provide a semiconductor pressure sensor which can be simplified in its own construction, and which can be assembled to the housing body in a more compact state.
For this object, according to a first aspect of the present invention, there is provided a semiconductor pressure sensor for detecting pressure of a pressure medium, the semiconductor pressure sensor having a semiconductor sensor element for pressure detection supported by a sensor body via a pedestal seat and being assembled to a housing body that partitions the pressure medium and outside from each other, wherein the sensor body is formed into a plate shape of a specified thickness having a flange portion, where the pedestal seat for joining and supporting the semiconductor sensor element and an adjustment circuit board for the semiconductor sensor element are joined on one surface side of the sensor body, and wherein the sensor body is fixed by being inserted into a stepped through hole provided in the housing body.
According to the first aspect of the present invention, in a semiconductor pressure sensor of the type that the adjustment circuit board for the semiconductor sensor element is provided separately from the sensor element, the sensor body is plate shaped and the adjustment circuit board is joined to this sensor body. Therefore, as compared with the conventional case in which this adjustment circuit board would be provided separately from the sensor body, the pressure sensor can be simplified in construction and reduced in parts number, which can contribute to a reduction in the manufacturing cost of the pressure sensor.
Also, since the sensor body is formed into a plate shape of a specified thickness having a flange portion and fixed by being inserted into the stepped through hole provided in the housing body, the sensor body can be fixed directly to the housing body in assembling the pressure sensor to the housing body, so that the assembling structure of the pressure sensor to the housing body can be simplified to a large extent, as compared with the conventional case in which the adjustment circuit board provided separately from the sensor body would be held by a holder provided in the housing body. In this case, the sealability between inside and outside of the housing body is ensured at the abutting surface between the flange portion of the sensor body and the stepped portion of the through hole of the housing body. Further, by appropriately setting the thickness of the sensor body in view of the thickness of the housing body, the extent to which the pressure sensor is protruded from the housing body surface can be made far smaller than the conventional counterpart. As a result of this, the assembled state of the pressure sensor to the housing body can be made very compact.
In a second aspect of the present invention, there is provided a semiconductor pressure sensor for detecting pressure of a pressure medium, the semiconductor pressure sensor having a semiconductor sensor element for pressure detection supported by a sensor body via a pedestal seat and being assembled to a housing body that partitions the pressure medium and outside from each other, wherein the sensor body is formed into a plate shape of a specified thickness having a flange portion, where the pedestal seat for joining and supporting the semiconductor sensor element having an output adjustment circuit is joined on one surface side of the sensor body, and wherein the sensor body is fixed by being inserted into a stepped through hole provided in the housing body.
According to the second aspect of the present invention, the sensor body is plate shaped and one type of semiconductor sensor element having an output adjustment circuit is used. As a result, the pressure sensor can be reduced in planar size and besides simplified in structure, while the parts number involved can be further reduced.
Furthermore, since the sensor body is formed into a plate shape of a specified thickness having a flange portion and fixed by being inserted into a stepped through hole provided in the housing body, the sensor body can be fixed directly to the housing body in assembling the pressure sensor to the housing body, so that the assembling structure of the pressure sensor to the housing body can be simplified to a large extent, as compared with the conventional case in which the adjustment circuit board provided separately from the sensor body would be held by a holder provided in the housing body. In this case, the sealability between inside and outside of the housing body is ensured at the abutting surface between the flange portion of the sensor body and the stepped portion of the through hole of the housing body. Further, by appropriately setting the thickness of the sensor body in view of the thickness of the housing body, the extent to which the pressure sensor is protruded from the housing body surface can be made far smaller than the conventional counterpart. As a result of this, the assembled state of the pressure sensor to the housing body can be made very compact.
In a third aspect of the present invention, there is provided a semiconductor pressure sensor according to the first or second aspect, wherein the sensor body is fixed by being caulked to the housing body.
According to the third aspect of the present invention, basically, the same effects as in the first or second aspect can be produced. In particular, since the sensor body is caulked and fixed to the housing body, the plate-shaped sensor body can be fixed to the through hole of the housing body easily and reliably, while enough fixing force to ensure the sealability between inside and outside of the housing body can be obtained.
In a fourth aspect of the present invention, there is provided a semiconductor pressure sensor according to the first or second aspect, wherein the sensor body is fixed by being tightened to the housing body with a screw.
According to the fourth aspect of the present invention, basically, the same effects as in the first or second aspect can be produced. In particular, since the sensor body is fixed to the housing body by being tightened with a screw, the plate-shaped sensor body can be fixed to the through hole of the housing body easily and reliably, while enough fixing force to ensure the sealability between inside and outside of the housing body can be obtained.
In a fifth aspect of the present invention, there is provided a semiconductor pressure sensor according to any one of the first to fourth aspects, wherein a seal member is provided between a stepped portion of the through hole of the housing body and the flange portion of the sensor body.
According to the fifth aspect of the present invention, basically, the same effects as in any one of the first to fourth aspects can be produced. Besides, since the seal member is provided between the stepped portion of the through hole of the housing body and the flange portion of the sensor body, the sealability between inside and outside of the housing body can be enhanced to a large extent. In other words, because enough sealability can be ensured by less fixing force, such problems as occurrence of strain in the sensor body due to the effect of the fixing force can be avoided more reliably.
Further, when there is a difference in thermal expansion coefficient between the housing body and the sensor body, it could occur that the sensor body is stressed by the housing body based on this difference. In such a case, however, the strain that could occur to the sensor body can be suppressed to a minimum by buffering the stress derived from the housing body. Moreover, occurrence of such problems as adverse effects on the output characteristics of the semiconductor sensor element can be effectively prevented.
In a sixth aspect of the present invention, there is provided a semiconductor pressure sensor according to the fifth aspect, wherein a protective mechanism for the seal member to protect the seal member from being excessively deformed is provided at either one of the stepped portion of the through hole of the housing body or the flange portion of the sensor body.
According to the sixth aspect of the present invention, basically, the same effects as in the fifth aspect can be produced. In particular, a protective mechanism for the seal member to protect the seal member from being excessively deformed is provided at either one of the stepped portion of the through hole of the housing body or at the flange portion of the sensor body. Therefore, upon the action of a fixing force with which the sensor body is fixed to the housing body, the occurrence of impairment of the sealability and the buffering performance due to excessive deformation of the seal member can be reliably prevented.
In a seventh aspect of the present invention, there is provided a semiconductor pressure sensor according to any one of the first to sixth aspects, wherein a reinforcing portion is formed on the other surface side of the sensor body.
According to the seventh aspect of the present invention, basically, the same effects as in any one of the first to sixth aspects can be produced. Besides, since the reinforcing portion is formed on the other surface side of the sensor body, the rigidity of the sensor body is enhanced. Therefore, upon the action of a fixing force with which the sensor body is fixed to the housing body or the action of pressure of the pressure medium, deformation of the sensor body and the resultant effect of stress on the semiconductor sensor element can be suppressed.
In an eighth aspect of the present invention, there is provided a semiconductor pressure sensor according to the seventh aspect, wherein the reinforcing portion is formed into a beam shape.
According to the eighth aspect of the present invention, basically, the same effects as in the seventh aspect can be produced. In particular, since the reinforcing portion is formed into a beam shape concretely, the sensor body is reinforced along this beam, thus being enhanced in its rigidity.
In a ninth aspect of the present invention, there is provided a semiconductor pressure sensor according to the seventh aspect, wherein the reinforcing portion is formed concentric with a pressure introducing hole to the semiconductor sensor element.
According to the ninth aspect of the present invention, basically, the same effects as in the seventh aspect can be produced. In particular, the reinforcing portion is formed concentric with a pressure introducing hole to the semiconductor sensor element concretely, the sensor body is reinforced concentrically with the pressure introducing hole, thus being enhanced in rigidity.